JPH0663060B2 - Method for manufacturing rolled aluminum alloy plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a molding for which strength and excellent molding workability, particularly bendability, are required for electric machine controller casings, measuring instrument casings, chassis for VTR and other weak electrical equipment, etc. The present invention relates to an aluminum alloy rolled plate used for a processed product.

2. Description of the Related Art In recent years, aluminum alloys have been often used for electric machine controller casings, measuring instrument casings, chassis for VTRs and other weak electrical equipments because of their light weight and electromagnetic shielding properties. In such applications, it is required that the strength and molding processability are excellent and the corrosion resistance is also good. Therefore, as the aluminum alloy sheet material for such applications, JIS 5000 series Al-Mg alloy rolled sheet is conventionally used. Is used, of which 503 alloy H3
4 Temper material is most often used.

Problems to be solved by the invention In the case of the 5052 alloy H34 material, although the bendability is relatively good, the plate thickness of about 2 mm is the limit of use in bending, and the 5052 alloy is used for the above-mentioned applications. There is a demand for a material that has better bendability and higher strength than the H34 material. In terms of strength, the 5082 alloy O material and the like are superior to the 5052 alloy H34 material, but are significantly inferior in bendability and are not practical for the above-mentioned applications.

The present invention has been made in view of the above circumstances, and as an aluminum alloy rolled plate used for the above-mentioned applications such as an electric machine controller housing, the strength and the bendability are higher than those of the conventional 5052 alloy H34 material. It is an object of the present invention to provide an excellent rolled aluminum alloy plate.

Means for Solving Problems The bendability of an aluminum alloy is better as the n value is better, the local elongation is better, or the second phase dispersed particles are finer among the various material properties. Although it has been found that the present inventors have particularly conducted experiments and studies on the bendability of Al-Mg alloys, the precipitates at the grain boundaries cause a significant deterioration of the bendability. I found that. That is, in the Al-Mg alloy, the β phase (Al ₃ Mg ₂ phase) has a strong tendency to preferentially precipitate at grain boundaries,
As described above, it has been found that if the β phase is precipitated at the grain boundary, the grain boundary strength is significantly reduced, and the bendability is significantly deteriorated. Therefore, if the β phase is prevented from precipitating at the grain boundaries at all, it is possible to dramatically improve the bend formability of the Al-Mg alloy. Therefore, as a result of further experiments and investigations, the present inventors have found that β
Higher than the precipitation temperature range of the phase, by actively heating to a specific temperature range in which Mg can be solid-dissolved, by rapidly cooling at a specific cooling rate such that the β phase cannot precipitate after the heating, It is possible to obtain a plate with no precipitation of β phase at the recrystallized grain boundary, and the aluminum alloy rolled plate thus obtained is actually found to have excellent bend formability and high strength, The invention was completed.

Specifically, the manufacturing method of the first invention is Mg3.0-6.0% by weight.
Containing Al and the balance being Al and unavoidable impurities
Using Mg-based alloy as a raw material, the required sheet thickness is obtained by hot rolling and / or cold rolling, and then heated to a temperature in the range of 450 to 550 ° C., and immediately or after holding for 120 seconds or less, It is characterized in that it is cooled at a cooling rate of 20 ° C./sec or more to obtain a rolled plate free of precipitates covering recrystallized grain boundaries.

In addition, the manufacturing method of the second invention, as a raw material, in addition to Mg3.0-6.0 wt%, Mn0.05-0.7 wt%, Zr0.01-0.2 wt%,
Using an Al-Mg based alloy containing one or more of Cr of 0.05 to 0.3% by weight and Cu of 0.10 to 1.0% by weight, the treatment is performed under the same conditions as in the first invention, It is characterized in that a rolled plate having no precipitate covering the grain boundaries is obtained.

Operation First, the reasons for limiting the alloy components of the raw material in the present invention will be explained.

Mg: Mg is an essential basic alloying element in the system alloy targeted by the present invention, and contributes to strength and formability. 3.0% Mg
If it is less than (% by weight, the same applies hereinafter), it is difficult to obtain strength higher than that of the conventional 5052 alloy H34 material, while if it exceeds 6.0%, high strength can be obtained, but castability and rollability deteriorate, resulting in mass production process. 3.0-6.0 as it is unsuitable for manufacturing in
It was limited to the range of%.

Mn: Mn is an element that contributes to the improvement of strength and is selectively added in the method of the second invention. If Mn is less than 0.05%, the effect of Mn addition is not sufficient, while if Mn exceeds 0.7%, DC
In the case of a cast material, the formability deteriorates. Therefore, in the second invention, Mn is limited to the range of 0.05 to 0.7%.

Cr: Cr is also an element contributing to the improvement of strength and is selectively added in the method of the second invention. If Cr is less than 0.05%, the effect of Cr addition cannot be sufficiently obtained, while if it exceeds 0.3%, coarse intermetallic compounds are generated in DC casting to deteriorate formability. Therefore, in the second invention, Cr is limited to the range of 0.05 to 0.3%.

Zr: Zr is also an element contributing to the improvement of strength, and is selectively added in the second invention. If Zr is less than 0.01%, the effect of Zr addition cannot be sufficiently obtained, while if it exceeds 0.2%, the recrystallization is delayed and the annealing temperature range is significantly limited, making it difficult to apply the process of the present invention. In the second invention
Zr was limited to the range of 0.01 to 0.2%.

Cu: Cu is an element that contributes to the increase in strength when added at the same time as Mg, and is selectively added in the second invention.
If the Cu content is 0.10% or less, the effect of Cu addition cannot be sufficiently obtained.
If it exceeds 1.0%, casting cracks are likely to occur and the corrosion resistance is also deteriorated. Therefore, in the second invention, Cu is limited to the range of 0.10 to 1.0%.

In addition to each of the above elements, F
e, Si are contained as unavoidable impurities. Although these are not particularly important elements in the present invention,
If the content exceeds 0.5%, the amount of crystallized substances that crystallize in the ingot stage increases and the bendability decreases.
% Or less is preferable.

Further, in addition to the above-mentioned elements, Ti, or Ti and B may be added in the same manner as a normal aluminum alloy in order to refine the ingot structure. However, in order to prevent the crystallization of primary TiAl ₃ particles, Ti is preferably 0.15% or less.
In order to prevent the formation of B ₂ particles, B is preferably 0.01% or less.

Next, the process in the method of the present invention will be described.

In the method of the present invention, the steps up to rolling may be the same as the conventionally known method. That is, an alloy having the above-described composition is cast by, for example, DC casting, and the obtained ingot is subjected to homogenization treatment by heating and holding at 450 to 500 ° C. for 2 to 48 hours, if necessary, and hot working according to a conventional method. The required plate thickness is obtained by rolling, or hot rolling and cold rolling.
Of course, intermediate annealing may be performed between the hot rolling and the cold rolling, or in the middle of the cold rolling, if necessary.

After rolling to the required plate thickness in this way, heating to a temperature range within the range of 450 to 550 ℃, immediately or after holding for 120 seconds or less, heat treatment to cool at a cooling rate of 20 ℃ / sec or more To do. This heat treatment is a characteristic step in the present invention, and by performing such heat treatment, an aluminum alloy rolled plate having no grain boundary precipitation is obtained.
That is, the temperature range of 450 to 550 ° C. is not only the recrystallization temperature range but also exceeds the β phase precipitation temperature range,
It is a temperature range in which Mg can be positively solid-dissolved, and after recrystallization while actively solidifying Mg by heating and holding in that temperature range, it is possible to prevent β-phase precipitation from that temperature range 20 ℃ / se
By cooling at a cooling rate of c or higher, it is possible to obtain a material in which the β phase is not precipitated at the recrystallized grain boundary. And, as described above, in Al-Mg alloys, β-phase grain boundary precipitation was a cause of deterioration of bend formability, but grain boundary precipitates were present in the rolled plate obtained by such heat treatment. Therefore, the bending formability is remarkably excellent.

Here, in order to obtain good bend formability, the heating temperature and cooling rate are important, and the heating rate has almost no effect on bend formability, and therefore the temperature rise to a temperature range of 450 to 550 ° C. The speed may be set arbitrarily.

If the heating temperature is lower than 450 ° C, recrystallization may be incomplete and good moldability may not be obtained.
If the temperature exceeds 550 ° C., the alloy composition targeted by the present invention causes coarse growth of crystal grains, and good formability cannot be obtained. Therefore, the heating temperature must be in the range of 450 to 550 ° C. Even within this range, a temperature range of 480 to 550 ° C is particularly desirable.

On the other hand, the heating and holding time of 120 seconds or less is regulated from the viewpoint of productivity rather than moldability. That is, it is preferable that the above heat treatment of the present invention is practically performed by applying continuous annealing in which the coil is continuously unwound while the coil is unwound. In this case, it is preferable that the holding time be long from the viewpoint of productivity. No, 120 seconds or less is appropriate. 450 ~
After reaching the temperature range of 550 ° C, cooling may be performed immediately without holding.

The cooling rate after heating is important along with the heating temperature,
If the cooling rate is slower than less than 1 sec / sec, the β phase precipitates at the recrystallized grain boundaries and the bending formability is remarkably deteriorated. Therefore, it is essential to set it to 20 ° C./sec or more.

Examples Alloys 1 to 7 shown in Table 1 were DC-cast according to a conventional method, then the ingot was subjected to homogenizing heat treatment at 500 ° C. for 4 hours, and further hot-rolled and cold-rolled according to a conventional method. A rolled plate having a plate thickness of 2.5 mm was obtained. Then, each rolled plate was heat-treated under the conditions A to M shown in Table 2.

For each rolled plate after heat treatment, mechanical properties (tensile strength,
(Proof strength, elongation), local elongation, n value, and minimum bending radius (Rmin) were evaluated for formability evaluation, and grain boundary precipitation was observed. The results are shown in Table 3. Here, the minimum bending radius is the minimum bending radius for 90 ° bending, which is shown as a ratio to the plate thickness. The state of grain boundary precipitation was determined by microscopic observation after etching with a 10% phosphoric acid etching solution at 25 ° C for 30 minutes or 50 ° C for 90 seconds.

As is clear from Table 3, when alloys 1 to 6 within the compositional range of the present invention were subjected to heat treatment within the range of the conditions of the present invention (A to F), there was no grain boundary precipitation. , The minimum bend radius is almost 0, and it has excellent bend formability.
Moreover, it was confirmed that the strength was sufficient.

On the other hand, when the composition is within the scope of the present invention, but the cooling rate during the heat treatment is slow (H, I, J and L)
It was found that the precipitation was found in the grain boundaries, and therefore the minimum bending radius was large and the bendability was poor. Here, the value of the minimum bending radius seems to be a numerically slight difference, but even a numerically slight difference causes a large difference in bending formability in actual bending, for example, R for plate materials with minimum bending radius (Rmin) of 2
If a 90 ° bending test is performed at = 0, a remarkably large crack is generated and it becomes unusable.

Further, the condition symbol K is an example in which the heating temperature during the heat treatment was too low, but in this case, recrystallization did not occur and the formability was remarkably lowered.

Furthermore, when the comparative alloy of alloy No. 7 having an Mg content of less than 3% was used, the heat treatment conditions were set within the scope of the present invention (condition symbol G), and the heat treatment conditions were set outside the scope of the present invention (conditions The symbol M) also has good bending formability,
It lacked strength.

From these results, the alloy rolling plate within the specific composition range was heated to a relatively high temperature range of 450 to 550 ° C.
It is clear that the heat treatment of rapidly cooling at 20 ° C./sec or more can provide a rolled plate excellent in both bend formability and strength.

EFFECTS OF THE INVENTION According to the method of the present invention, strength and formability, in particular, as an Al-Mg-based aluminum alloy rolled plate used for a molded product requiring bending formability, β phase precipitation at grain boundaries By suppressing the above, it has significantly better bend formability than the conventional 5052 alloy H34 material, etc.
It is possible to obtain a rolled aluminum alloy plate having high strength equal to or higher than that of H34 material and the like.

Front Page Continuation (72) Inventor Takeshi Kajiyama 4-chome, Nihombashi Muromachi, Chuo-ku, Tokyo Inside Sky Aluminum Co., Ltd. (56) References JP 61-6244 (JP, A) JP 58-171547 ( JP, A) JP 57-98648 (JP, A) JP 57-131352 (JP, A)

Claims (2)

[Claims] 1. An Al-Mg based alloy containing 3.0 to 6.0% by weight of Mg, the balance being Al and unavoidable impurities.
20 ℃ / sec after making the required plate thickness by hot rolling and / or cold rolling, then heating it to a temperature in the range of 450-550 ℃ and holding it for 120 seconds or less immediately.
A method for producing a rolled aluminum alloy plate having excellent bend formability, which comprises cooling at the above cooling rate to obtain a rolled plate free of precipitates covering recrystallized grain boundaries. 2. It contains Mg3.0-6.0% by weight, and Mn0.05-
0.7 wt%, Zr0.01-0.2 wt%, Cr0.05-0.3 wt%, C
u 0.10 to 1.0% by weight of one or more kinds of Al-Mg base alloy containing Al and unavoidable impurities in the balance is used as a raw material, and required by hot rolling and / or cold rolling. Plate thickness, then heat to a temperature in the range of 450 to 550 ℃, hold immediately or for 120 seconds or less, then cool at a cooling rate of 20 ℃ / sec or more to cover the recrystallized grain boundaries. A method for producing a rolled aluminum alloy sheet having excellent bend formability, which comprises obtaining a rolled sheet having no material.